1. Field of the Invention
This invention relates to the field of drilling, reaming, and cutting tools and methods, in particular, to the drilling, reaming, and cutting of subterranean formations.
2. Background Summary
There are massive costs associated with drilling below the earth's surface on land and the sea floor. These costs can broadly be grouped into two categories: capital costs and expenses. Capital costs tend to be one time costs of equipment including, but not limited to, the drilling platform, drilling rig, pump, drill pipe, trucks, tractors, and buildings. Expenses tend to be hourly costs or consumable material including, but not limited to, wages, food and lodging, electricity, water, fuel, equipment rentals, drill bits, drilling mud, geological and geophysical services, cementing services, down-hole tool services, completion and production services, and transportation.
As drilling takes place these costs can be compounded by difficult formations. These difficult formations may include, but are not limited to, hard formations such as granite which wear out drill bits rapidly, sticky formations such as gumbo soil which can adhere to a drill bit and render it ineffective, and combinations of these and other formations. These difficult formations frequently dictate that the driller trips out of the well, corrects the problem by replacing a worn or ineffective bit and then trips back into the well. These round trips in and out of the well are time consuming and costly, often taking many hours, during which time no drilling can occur, while most capital costs and expenses will continue.
In addition to the massive costs of successful drilling operations, there are additional costs associated with problems which may, and often do, arise while drilling. These problems and their associated costs may include, but are not limited to, collapsed wells and broken drill strings resulting in abandonment of the well.
Difficult formations and trips in and out of the well significantly reduce the rate of penetration (ROP) and introduce a dilemma for the driller regarding weight on bit (WOB) caused by the bit contacting the formation. To improve ROP, the driller can increase the WOB to drill hard formations faster, but the drill bit will wear out faster and result in more trips in and out of the well.
None of the current tools and methods described above has provided adequate improvements to the dilemma of WOB, massive costs, and ROP, collectively. The invention described herein significantly improves the collective WOB, cost and ROP deficiencies of the prior art.